Shockproof x-ray tube



ay 12, T936. c. M. sLAcK ET AL 2,040,155

` SHOCKPROOF x-RAY TUBE Filed Nov. 30, 1954 5 Sheets-Sheet l ATTORNEY l`c. M. SLACK ET Al.

SHQCKPROOF X-RAY TUBE 3 sheets-`slheet 2 Filed Nov. 5o, 1954 mwww wwwwww WW ww K N n@ www ww www www N w S5 n RaaRfW-luililllllilllll:liu

lnoted copending application.

Patented May 12, 1936 UNITED STATES PATENT OFFICE r SHOCKPROCF X-RAYTUBE Sylvania Application NovemberV 30, 1934, Serial No. 755,332

6 Claims.

Our invention relates to X-ray apparatus and has particular reference toshockproof X-ray apparatus wherein the danger of accidental shocksresulting to a patient or operator are entirely eliminated andconstitutes an improvement on the apparatus shown and described in thecopending application of C. M. Slack, Serial No. 750,760, led October3l, 1934.

The most common type of shockproof X-ray apparatus at present utilizedin the art is that of the so-called oil immersed type wherein the X-raytube and the high tension transformer for supplying the energy theretoare immersed in a cooling and insulating material and encased in ametallic housing.

Such oil immersed apparatus, however, has several inherent objectionablefeatures which it is preferable to eliminate. For example, the en tireweight thereof renders it exceedingly unwieldy and difficult tomanipulate and the insulating material acts as a lter for the gen-Aerated X-rays. Accordingly a shockproof unit obviating the undesirablefeatures of the oil immersed type is shown and described in the aboveThis apparatus comprises an X-ray tube having a foreshortened lengththan that normally required for a tube operating in air at the sameapplied voltage, and the energy for the tube is supplied by groundedmetallic sheathed cables, which are connected to recessed electrodeterminals carried by the envelope in such manner, as to insulate thesame and prevent spark over to grounded metallic parts of the apparatusat the maximum operating voltages of the tubes.

Cur present invention is concerned primarily with the provision of asimilar type of shockproof unit wherein the energy `is supplied throughgrounded metallic sheathed cables which in addition to supplying the`energy so support the tube that the same may be rotated to variousinclinations for the purpose of treating or radiographing various partsof the anatomy.

It is accordingly an object of our present invention to provide a cableconnected vshockprooi" unit wherein the X-ray tube isof a foreshortenedlength than that normally required for a tube operating in air at thesame applied voltage and the Unit is rotatable about its longitudinalaxis With the high tension cables which supply the electrical energyfunctioning as bearings for the. rotation thereof.

' Another object of our present invention is the' provision of a cableconnected shockproof unit wherein the X-ray tube is of a foreshortened(Cl. Z50-35) length than that normally required for a tube operating inair at the same applied voltage with the energy for the tube beingsupplied through grounded metallic sheathed cables and the unit beingrotatable about its horizontal axis to allow directing of the radiationsat various inclinations of the unit.

Another object of our present invention is the provision of a cableconnected shockproof unit wherein the X-ray tube is of a foreshortenedlength than that operating in'air at the same applied voltage with theenergy for the tube be-` ing supplied through grounded metallic sheathedcables which enter the ray proof housing and are so connected to theterminals of the X-ray tube as to reduce the spacing normally requiredbetween the tube terminals and the grounded housing, and wherein theunit is' rotatable to various inclinations about the cables whichfunction as bearings for rotation thereof.

Another object of our present invention is the provision of a cableconnected shockproof unit wherein the energy for the tube is suppliedthrough grounded metallic sheathed cables connected to the ray proofmetallic housing and the X-ray tube terminals in such manner as toVground the housing and form a support for the tube about which the tubeand housing may rotate as a unit, as well as to form suicient insulationfor the tube terminals so that the actual air gap spacing between thelatter and the grounded housing may be reduced, to enable theutilization of a tube of foreshortened length than that normallyrequired for a tube operated in air at the same applied voltage.

A further object of our present invention is the provision of a cableconnected shockproof' unit wherein the X-ray tube is of a foreshortenedlength than that normally required for a tube op` erating in air at thesame applied voltage, with the energy for the tube being suppliedthrough grounded metallic sheathed cables connected to the ray proofmetallic housing and extending into the tube, so as to insulate theelectrode terminals to prevent spark-over to the grounded housing andforming a longitudinal axis about which the tube and housing may berotated to` various inclinations, and a circulatory system is providedfor the cooling of the anode of the X-ray tube in all inclinations ofthe latter about the longitudinal axis formed by the cables.

Still further objects of our present invention will become obvious tothose skilled in the art by reference to the accompanying drawings,

wherein:

Figure 1 is a side view of a shockproof unit constructed in accordancewith our present invention.

Fig. 2 is a side view in cross section and on an enlarged scale of theapparatus shown in Fig. 1.

Fig. 3 is a sectional view on a still further enlarged scale of aportion of the unit as shown in Fig. 2.

Fig. 4 is a sectional View taken on theV line IV-IV'of Fig; 3.

Fig. 5 is a sectional View taken on the line V-V of Fig. 3.

Fig. 6 is a sectional View showing-a -portion of a modification of theunit as shown in Fig. 2 with parts thereof broken away to betterillustrate the unit.

Fig. 'I is a sectional view of astill further portion of themodification shown in-Fig. 6 and constitutes the right hand end'v of theunitwhich' is broken away in the preceding figure.

Fig. 8 is a sectional View taken on the line VH1-VIII: of Fig. 6, and

Figl-Q istaisectional view' taken on the line IX-IX of Fig.` 6.

Referring now tothe drawings in detail and particularly to Figs.. 1 and2 thereof we have shown.` an` X-ray tube` comprising an elongatedevacuated vitreous envelope 5 of a'foreshortened length than thatinormally required for a tube operati-nginair at thesame applied voltage.A metallic or otherl suitable ray opaque housing, shown generally. at.16,V surrounds the X-ray tube for' preventing the egress of X-raysexcept throughfa pervious window 'I` provided inthehousingas-hereinafter more fully set forth.

rIhis envelope lis provided withreentrant stems BlandfS-extending wellinto the envelope as can be more-readily seen in Fig. 2 with theinnermost portion; of. the. reentrant` sleeve 8. being formed into-apress- I through which a pair of conductors- I I and I 2 passi-to. thecathode electrode shown generally'at. I3.v

'IT-hisVv latter electrode comprises the usual filament I4 (Fig. 3)which is recessed within a focusing-cupor shield L5, inturnvtting overthe press portion.Y off the reentrant sleeve 8, and held inV place-bymeans of metallicf'rings-or the like I6. An'insulateddisc I-I issuitably secured to the inner periphery of the reentrant steml 8, at theinnermost extremitythereof and is provided with apair ofrecessedmetallic sleeves I8y and I9-which are: connectedrtoAthefllament. I 4 by the conductors |I` and I2 passing through the pressand thus constitutesf-thecathode terminal for the tube.

A hollow-anodeelectrode2El-formedy of a material of good electricaland`thermalconductivity, such asy copper or the like, and provided'with theusual target 2| of.V refractory metal embedded` in the'head thereof,is-sealed by a feather edge copper annulus 2'2rto thev reentrant portion9 of the envelope Av vitreous glass sleeve 23fused to the envelope isdisposed interiorly thereofand.

extends=.longitudinally from well in back of the point. of sealof theanode to the envelope to considerably beyond` the press I0 formed in thereentrant steml 8. This-sleeve is provided with constrictions-Z adjacentthe anode and cathode for apurpose shown and. described` more in detailin thefcopending application of C. M. Slack, Serial Nos'lled. October30, 1934, `but as the same pei: se formsno part of out present inventionfurther descriptionthereof is deemed unnecessary.

The hollow anode. 29 is threaded at the outer end asshowniin Fig;3,.andis arranged to be engagedlby afmetallicmember 26 formingv an oil tightconnection. This latter member 26 is provided with a portion of reduceddiameter intermediate its ends which forms an annular passage Z'Icommunicating through a plurality of radial openings 28 with alongitudinal passage 29 interiorly of the member 26.

A further metallic member 36, having an elongated portion 3| of reduceddiameter, is arranged to threadedly engage the member 26 at its outerextremity as well as interiorly thereof in an oil tight manner, to forman integral member having the annular passageway 29 interiorly thereof,between the portion 3| of the member 39 and the greater portion of theinterior of the member 26. This latter member 36 is provided with arecess 33 forming an anode terminal for the X- ray tube similar to thecathode terminal which comprises the insulated disc I'I and sleeves I8and I9.

A longitudinal passage 34 is provided interiorly of the member 36 whichextends through the portion 3| of reduced diameter and registers with aportion of the passage 29 adjacent theY rear surface of the anode head.A pair of angularly extending passageways 35 and 36 are pro-- vided inthe member 36 one of which, 35, aligns with the longitudinally disposedpassage 34 and the other, 36, communicating with the annular passage 29.A suitable tting, such as an elbow 3.1 of insulating material,threadedly engages the anode terminal member 30 in alignment with thegj.;

angular passageway 35.

An inlet. conduit 38 also of suitable insulating material extends froman appropriate reservoir (not shown) which in turnengages the elbow 3'Ithus forming a continuous inlet passage from the ;y

reservoir to the interior of the hollow anode 26 for the ingress of acooling and insulating material, such as oil, with the insulationcharacteristicsof this oil being augmented by the insulated elbow 31 andthe conduit 38` so that the potential applied to the anode will not betransmitted to other parts of theV apparatus by the cooling sysstem.

In a` similar manner an insulated elbow 39 threadedly engages the anodeterminal member 39 in alignment with the angular passageway 36 and anoutlet conduit 46 extends from this elbow back to the reservoir.Accordingly during operation of the tube the oil or other suitableinsulating material will ow from the reservoir mediately in back of thetarget 2| at the point of g' greatest heat. concentration. The oil thenflows around the member 26 through the annular passage 2'I and radialopenings 28 to the annular passageway 29 formed bythe union of themembers 26 and 36. As the angular passageway 36 communicates with thepassageway 29 the oil flows therethrough and returns to the reservoirthrough the insulated elbow 39 and return or loutlet conduit 40.

The metallic housing, shown generally at 6 as before stated, may beformed in sections to facilitate assembly of the tube therein and maycomprise a center section 4| having the ray pervious window 'I and alining 42 of a metal .of high atomic weight, such as lead, for shieldingpurposes, and n' in order to prevent undue shocks to the tube a pair ofcushion rings or the like 43 may be carried bythe section 4| which bearlightly against the envelope 5. An end section 44 is arranged tu overlapthe center section 4| and is provided with an annular shoulder portion45 bearing against the end of the center section for longitudinallypositioning the same, and is held in place in any suitable manner, suchas by cap screws or the like 46. This end housing section 44 has aninsulating sleeve 41 extending longitudinally thereof to well within thereentrant sleeve 9 of the envelope and is made an integral part of thehousing by `the provision of an annular shoulder 48 bearing against theend of the metallic portion of the section 44 with this sleeve beingrigidly secured to the latter, such as by means of a locknut or ring 49.At the inner end thereof the intern-al diameter of this sleeve isslightly reduced, as shown more clearly at U in Figs. 2, 3, 5 and 6, toform a bearing for a purpose to be hereinafter explained. Accordinglythis sleeve 41 .of insulating material, by extending well into thereentrant sleeve 9 of the tube, reduces the normal air gap spacingrequired to prevent sparkover between the anode terminal 30 and themetallic portion of the housing 44 at the maximum operating voltages ofthe tube, and is also provided with longitudinal passages through whichthe insulated conduits 38 and 40 pass to the exterior of the housing tothe reservoir.

A further end housing section 5| overlaps the center section 4I and issecured thereto in the same manner as just described relative to thesection 44, namely, by the provision of a shoulder 52 and cap screws orthe like 53. This section 5| is likewise provided with an insulatingsleeve 54 extending well into the reentrant sleeve 8 of the envelopehaving the bearing portion 56, and

is made an integral part of this housing section 5|, by being rigidlysecured thereto through a shoulder 55 and locking ring 56 constructed inthe identical manner as above noted with respect to the section 44, theonly dilierence between the two sections 44 and 5| residing in theprovision of an annular groove 51 at the end Aof the sleeve 54 whichextends substantially around the inner edge thereof for a purpose to behereinafter more fully described.

In order to support the tube and housing as well as supply highpotential electrical energy to the tube a pair of grounded metallicsheathed high tension cables 58 and 59 extend from a suitable source,such as a high voltage transformer (not shown) having the midpoint ofits secondary winding grounded, to the X-ray tube.

'Ihe cable 59 has the metallic sheathing removed therefrom a distancecorresponding to that from substantially the outside of the housing tothe recessed anode electrode terminal 30 which is disposed at theinnermost extremity of the reentrant sleeve 9. A sleeve of insulatingmaterial 60 ts snugly the unsheated portion of the cable 59 andaccordinglyv forms an integral part thereof. 'I'his sleeve 60 slidably.engages the insulated sleeve 41 at the bearing portion 5U providedtherein and also at the outer extremity, by an increased diameterportion 6I again forming a second bearing thus enabling rotation of thetube and housing about the cable 59.

For the purpose of supplying electrical energy to the anode electrodeterminal 30 as well as to form a further bearing for rotativelysupporting the unit, the sleeve 60 is closed at its inner end by aninsulated disc 62 provided withv a metallic pin 63 which is connected tothe electrical conductors 64 of the cable 59 and arranged to slidablyengage the recess 33 of the anode electrode terminal 30. A flange 65frictionally contacts the metallic sheathed portion of the cable andthreadedly engages the insulated sleeve portion 41 of the housing yetwhen completely screwed in place establishes an electrical contact withthe locking ring 49 for the purpose of effectively grounding themetallic housing and maintaining the cable in place within the reentrantsleeve 9 of the tube, as well as supporting one end of the tube andhousing.

In a similar manner the cable 58 is provided with an insulated sleeve 66forming an integral part thereof, which slidably engages the housingsleeve 54 at its bearing portion 58, and it is likewisel provided withan additional bearing 61 formed by an increased diameter portion in thesame manner as just described relative to the sleeve 66, with the cablebeing held in place by a flange 68 identical to that of the flange 65for effecting the ground connection to the metallic housing. The sleeve66 has a laterally extending pin 69 projecting into the annular groove51 so as to limit the rotation of the tube and housing about thelongitudinal axis formed by the respective cables 58 and 59 to slightlyless than 360 degrees.

The inner end of this sleeve 66 is provided with a loose fittinginsulated thimble 18 (Fig. 3) which constitutes an integral part of thesleeve 66 and cable 58 and is held in place by a locknut or the like 1Ihaving openings 12 adapted to be engaged by a suitable tool forinserting the nut in position. This thimble in turn is provided with apair of metallic pins 13 and 14 connected to the electrical conductorsvand 16 of the cable 58, and slidably engaging the metallic sleeves I8and i9 for the purpose of supplying low tensionV heating current to thelamentary cathode I4 as well` as one side of the high potential energythereto.

In the assembling of our unit the tube may be placed in the centerhousing section resting upon the cushion rings 43 with the conduits 38and protruding therefrom. The right hand end section 44 is then slid on,with the conduits 38 and 4U passing through the openings provided in theinsulated sleeve 41, and this section secured to the center section ofthe housing after the shoulder abuts the same by the screws 46. The lefthand end section 5| is then slid over the tube until the shoulderportion 52 contacts the center section 4| after which it is secured inplace by the set screws 53. This accordingly positions the insulatedsleeves 41 and 54, which form an integral part of the respective endsections 44 and 5I, well into the reentrant sleeves 8 and 9 of theenvelope and, as before stated, form suilicient insulation between therecessed electrode terminals I1 and 3-9 and the grounded metallichousing to enable the spacing therebetween to be reduced below thatnormally required for a tube operating in air at the same appliedvoltage thus resulting in the utilization of an X-iay tube 5 offoreshortened length.

The cables 58 and 59, having their respective integral sleeves 66 and 60secured thereto, are then slid into the sleeves 54 and 41, respectively,with the pins 13 and 14 engaging the metallic seeves I8 and I9, and thepin 63 slidably engaging the recess 33 in the anode terminal 30. Thisaccordingly connects the cables to the anode and cathode electrodeterminals of the X-ray tube 5 and at the same time supports the tube atthese electrodes as well as the housing at the bearing portions 50, 6Iand 61. The respective flanges 65 and 68 are then tightened thusestablishing a metallic connection between the grounded metallicsheathed portion of the cables 58 and 59 and the housing, showngenerally at 6 in Fig. 1, and

the conduits. 38 vand 48 arec'onnected' to the reservoir in any suitablemanner to allow a slight flexibility thereof.

During a radiographic examination or a therapeutic treatment theoperator may desireto alter the angle at which the X-rays strike thepatient. In this event it is only necessary to rotate the unit until theray pervious window 'I is' at the desired inclination as the cables 58and 59 remain stationary. The housing will, accordingly, rotate aboutthe cables 58 and 59 at the point of contact of the frictionally engagedflanges 65 and 58 with the metallic sheathing of the cables, and at thebearings 58 formed by reduced diameter portions of the sleeves @i and54, as well as at the points 6I and 61. At the same time the X-ray tubewill likewise rotate with the housing about its respective electrodeterminals which function as bearings therefor due to the slight frictionexerted by the cushion rings 43 and the engagement of the conduits 38and 49 with the insulated sleeve 47.

However, the metallic pins i3 and 14, which engage the cathode terminalsleeves I8 and I9, will also cause the thimble I8 to rotate with theX-ray tube, thus tending to twist the cathode heating conduct-ors 'I5and l2 as well as the cooling system conduits 38 and I9 if the unit isrotated completely 360 degrees. Such result is prevented by the pin 69projecting into the annular groove 5l because this latter groove doesnot extend completely around the end of the insulated sleeve 54 andaccordingly forms a stop limiting rotation of the entire unit, as beforestated, t slightly less than 360 degrees.

In Figures 6 to 9 inclusive we have shown a modification of thestructure just described which enables unlimited rotation of the unit ineither direction of rotation without interfering in any way with thecirculating system for cooling of the anode or causing a twisting of thecathode heating conductors l and 18. The unit in this particularembodiment is in most respects identical to that previously describedwith the exception of the construction of the electrode terminals andthe circulatory system. The insulated disc I1 in this particularmodification is again provided with the recessed metallic sleeve I8which in this instance is disposed concentric with the longitudinal axisof the X-ray tube 5 and metallic ray proof housing 6. In lieu of therecessed sleeve I9 as in the preceding construction, we provide arecessed metallic ring 88, shown more clearly in Figs. 6 and 8, which,like the metallic sleeve I8, is electrically connected to the lamentarycathode I4 by the conductors II and I2 passing through the press portionI0 of the reentrant sleeve 8.

The insulated sleeve 66 forming an integral part of the cable 58, isprovided with metallic pins 8I and 82 rigidly secured thereto andconnected to the conductors 15 and 16 of the cable 58. The pin 8lslidably engages the recessed concentric metallic sleeve I8 and the pin82 which is of a distorted ellipsoidal configuration, slidably engagesthe recessed metallic ring 88 so that upon rotation of the X-ray tubeand housing about the stationary cable 58 the pin 8l functions as aconcentric bearing and the pin 82, while not concentrically disposed,nevertheless also functions as a bearing enabling rotary motion of thering 88 without destroying the electrical contact therebetween. Hence,upon rotation of the unit the entire cable 58, including the metallicpins 8| and 82, remains stationary thus precluding any possibility oftwisting ofthe conductors 'I5 and 16.

Also in this modification, as shown particularly in Fig. 6, the hollowanode 20 isagain threaded at the outer end and is arranged to be engagedby a metallic member 83 of substantially frustoconical configurationhaving a portion of reduced diameter intermediate its ends which formsan annular passage 84. This passage 84 communicates through a pluralityof radial openings 85 with the hollow interior of the member 83. Ahollow metallic member 86, having substantially the same conguration asthe member 83 but of slightly reduced size than the hollow interior ofthe latter member, threadedly engages the same until a shoulder 8lcarried by the member 86 bears rmly against the member 83 and forms anoil-tight seal therebetween. This accordingly forms an annular passage88 between the interior surface of the member 83 and the exteriorsurface of the member 86 while at the same time completinga passageway89 communicating from the interior of the hollow member 86 to the end ofthe member 83 immediately in back of the anode head carrying the target2 I A third metallic member 98 of substantially conical form in turnissecured to the member 86 in an oil-tight manner thus closing the openend of the member 88 and converting the hollow passageway 89 of themember 86-into lannular form for a portion of its length. In order toestablish a communication to the passageway 89 the member 98 is providedwith a series of longitudinally extending openings 9i, as can be morereadily seen in Figs. 6 and 9, which align with the annular formedportion of the passageway 89, and this member 98 is provided with therecess 33 which forms the anode terminal in the same manner as justdescribed relative to the preceding embodiment of Y our invention.Moreover, while we have described the members 83, 88 and 98 as separateparts, it is to be understood that rial in the same manner as previouslydescribed A relative to Figs. l tor 5 inclusive.

An insulated sleeve 92 threadedly engages the metallic member 83, whichextends'longitudinally of the reentrant sleeve 9 of the envelope 5 in asimilar manner to the sleeve Min Fig. 2, and adjacent its free end isprovided with an annular shoulder 93 to which the right hand metallicend section 44 of the housing is secured in a suitable manner such as byset screws 94, thus enabling this sleeve to protrude slightly beyond thehousing section 4d where its internal diameter may be slightlyincreased, .as shown at 95. Another insulated sleeve 96 concentric withthe sleeve 92, but of slightly less diameter than the latter for thegreater part of its length, threadedly engages the metallic member 86thus forming an annular passage 91 therebetween which communicates withthe passage 88 between the metallic members 83 and 88.

This sleeve 98 projects slightly beyond the free end of the sleeve 92where its outer diameter increases in steps to that of the sleeve 92thus forming, with the provision of a gasket 98, an oiltight connectionas well as enabling the sleeve 92 to slightly overlap this sleeve 96 andsupport the same. A portion 99 of increased internal diameter isprovided in this sleeve 96 and its free end is provided with an annulargroove |00 for purposes hereinafter noted. A still further sleeve ingand connected to said electrode terminals for the purpose of supplyingelectrical energy thereto and for insulatingly supporting said X-raytube and housing to enable rotation of said tube and housing as a unitto various inclinations about said means, and to prevent the formationof corona or a discharge between said electrode tertminals at themaximum operating potential of said tube, and means connected to theelectrode terminal for said hollow anode for circulating a cooling andinsulating medium therethrough in all various inclinations of said X-raytube and housing.

3. A shockproof X-ray apparatus comprising an X-ray tube having anenvelope of foreshortened length than that normally required for a tubeoperating in air at the same applied voltage and' provided withoppositely disposed reentrant stems extending a substantial distancelongitudinally of said envelope, electrode terminals disposed at theinnermost extremity of said reentrant stems, an X-ray opaque housingsurrounding said X-ray tube and provided with a pervious window therein,and means for supporting said X-ray tube and housing to form alongitudinal axis about which said tube and housing may be rotated tovarious inclinations and for supplying electrical energy to said X-raytube comprising grounded metallic sheathed cables having an insulatedportion extending into said reentrant stems and connected to saidelectrode terminals, to form bearings for the rotation of said tube andhousing and to provide sufcient Vinsulation between said electrodeterminals and grounded parts of said apparatus to enable the spacingtherebetween to be reduced from that normally Arequired for a tubeoperating in air at the same applied voltage without the iormation ofcorona or spark-over resulting at the maximum operating voltage of saidtube.

4. A shockproof X-ray apparatus comprising an X-ray tube having anenvelope of foreshortened length than that normally required for a tubeoperating in air at the same applied voltage and provided withoppositely disposed reentrant stems extendinga substantial distancelongitudinally of said envelope, electrode terminals disposed at theinnermost extremity of said reentrant stems, an X-ray opaque metallichousing surrounding said tube and provided with an X-ray pervious windowtherein, and means for supporting said X-ray tube and housing and forsupplying electrical energy to said X-ray tube comprising groundedmetallic sheathed cables connected to said housing to ground the latterand provided with an insulated portion extendingv into said reentrantstems for supplying electrical energyto said electrode terminalsandforming an axis for said X-ray tube to enable rotation thereof and saidhousing as a unit to various inclinations.

5. A shockproof X-ray apparatus comprising an X-ray tube provided with athermionic cathode provided with portions extending into said housextending a substantial distance longitudinally 5 thereof, electrodeterminals for said anode and cathode disposed at the innermost extremityof said reentrant stems, an X-ray opaque housing surrounding said X-raytube provided with a pervious window therein, means for supporting 1()vsaid X-ray tube and housing to form a longitudinal axis about which saidtube and housing may be rotated to various inclinations and forsupplying electrical energy to said electrode terminals comprisinggrounded metallic sheathed l5',

cables having an insulated portion extending into said reentrant stemsto provide suiicient insulation between said electrode terminals andgrounded parts of said apparatus to enable the spacing;

therebetween to be reduced from that of the 2m normal air-gap equivalentfor the same applied voltage, and means connected to the electrndeterminal for said hollow anode for circulatigiga, cooling and insulatingmedium therethrough-zand;

through said hollow anode in all various inclina- 252 tions of saidX-ray tube and housing during operation thereof and to prevent thepotential'impressed upon said anode from being transrnitted to otherportions of said apparatus.

6. A shockproof X-ray apparatus comprisingti an X-ray tube provided witha thermionic cathode and a hollow anode and having an envelope oil'foreshortened length than that normally required; for a tube operatingin air at the same appliedI voltage with oppositely disposed reentrantstems 352 extending a substantial distance longitudinally thereof,electrode terminals disposed at the innermost extremity of saidreentrant stems, an X-ray opaque metallic housing surrounding said tubeand provided with an X-ray pervious window 40a therein, means forsupporting said tube and housing to form a longitudinal axis about whichsaid tube and housing may be rotated as a unit to various inclinationsand for supplying electrical,

energy to said electrode terminals comprising 45 grounded metallicsheathed cables connected to said housing to ground the latter andprovided with an insulated portion extending into said reentrant stemsto provide sufcient insulation between said electrode terminals andgrounded parts 50 of said apparatus to enable the spacing therebetweento be reduced from that of the normal air-gap equivalent for the sameapplied voltage, and means connected to the electrode terminal for saidhollow anode for circulating a cooling and insulating mediumtherethrough and through said hollow anode in all various inclinationsof said unit during operation thereof and operable to prevent thepotential impressed upon said anode from creating a potential stressbetween said means and grounded metallic portions of said apparatus.

CHARLES M. SLACK. ALFRED H. LAIDIG.`

